Heat-treatment of titanium-copper alloys



Unite HEAT-TREATMEN T F TITANIUM COPPER ALLOYS No Drawing. Filed Jan. 26, 1959, Ser. No. 788,793

Claims priority, application Great Britain Jan. 29, 1958 10 Claims. c1. 14s 12.7

This invention relates to a method of heat treating titanium alloys containing copper.

Alloys of titanium containing copper have been disclosed and it has also been proposed to heat treat such alloys by age-hardening methods. Various temperatures and periods of treatment produced only relatively small changes in hardness in a titanium-copper alloy. In addition such alloys have been reported to undergo overageing after comparatively short ageing times of the order of 2 hours.

The object of the present invention is to provide a method of heat treating titanium-copper alloys whereby improved properties are obtained.

According to the invention there is provided a method of treating a titanium-base alloy containing between 0.9% and 2.6% of copper, balance titanium apart from impurities, which comprises heating the alloy to a temperature between 750 C. and 1000 C. for a period of not less than 5 minutes and cooling the alloy at a rate sufficient to retain the alloy constituents in solid solution. Such a process is hereinafter referred to as solution treatment.

Alloys treated in accordance with this aspect of the invention have improved elevated temperature properties compared with similar alloys subjected to a preliminary annealing treatment at a temperature outside the above range.

By way of example, a titanium-2% copper alloy, solution-tre-ated at, 800 C. has, when tested at 220 C., an ultimate tensile strength of 27.5 tons/ sq. in., a 0.1% proof stress of 19.8 tons/sq. in. and an elongation of 31%, whereas, a similar alloy solution-treated at 800 C. and then annealed for /2 hour at 655 C. has an ultimate tensile strength of 22.9 tons/sq. in., a 0.1% proof'stress of 15.0 tons/sq. in. and an elongation of 23%.

According to a feature of the invention, the alloy, after cooling, is heated to a temperature between 300 C. and

600 C. for a period between. and 1000 hours.

Improvements in tensile properties and hardness associated with good ductility and good creep and fatigue properties are obtained by subjecting the alloy to both solution-treatment and ageing-treatment.

Thepreferred range of composition is 1.8 to 2.2% copper. The interstitial impurity content of the alloy may vary between wide limits without loss of agehardenability. Taking the hardness of the titanium starting material as a measure of oxygen and nitrogen content, age-hardening has been observed between'the "limits 70 and 200 on the Vickers scale of hardness numerals, the preferred range being 120 to 160 Vickers Diamond Pyramid Hardness Numerals.

States Patent 0 The heat treatment may be carried out in air or in a.

' in particular, sheet. It is advantageous in the case of ICE tion-treated alloy consists essentially of equiaxed grains of the alpha phase, but the presence of a small quantity of the beta phase may be beneficial. The preferred range is therefore 780 to 810 C. The duration of the solutiontreatment may be any period in excess of 5 minutes, preferably between 10 minutes and 1 hour. After solutiontreatment the alloys may be water-quenched or air-cooled without significant change in the age-hardening. characteristics. V V

Age-hardening may be carried out at any temperature between 300 C. and 600 C. but the preferred temperatures are those between 350 C. and 450 C. For any given ageing temperature, the hardness peak may be reached in times varying between 4 hour and 1000 hours, but the preferred ageing time is 10 to 300 hours. Some improvement in hardness over that obtained by ageing for the preferred time may be brought about by ageing for prolonged periods of up to 1000 hours. At the end of the ageing treatment, the alloys may be water-quenched or aircooled, i.e. allowed to cool at a natural rate in air.

Annealing to soften the material, intermediate between rolling passes, may be carried outin therange 650 C. to 750 C. for periods of /2 hour to 2 hours. Solution-treatment and ageing may afterwards he carried out. In Table I are given details of various treatments in accordance with the invention and the effects of varying different factors such as composition, temperature and times. Except where indicated in the first column of this table, the titanium raw material used to make the alloys was within the preferred range of hardness to 160 Vickers D .P.N.).

The ultimate tensile strength, proof stress and ductility in the solution-treated condition indicate that the alloys can be rolled easily in that condition. On ageing, increases in proof stress and ultimate tensile strength occur corresponding to the increase in hardness.

Table II shows the tensile properties of a titanium-2% copper alloy solution-treated in the alpha-phase field and aged for 238 hours at 400 C. It will be observed that, on ageing, there is an increase in strength without significant loss of ductility.

Whilst improved properties are conferred upon the alloy by the solution-treatment and ageing procedure discussed above, a reduction of the ageing period is produced by cold working the alloy after the solution-treatment. Reductions of between 2 and 25% accelerate ageing so that the preferred ageing period is decreased by a factor of .between 2 and 4. It has been found that after solutiontreatment and cold working to effect 10% reduction, an

EXAMPLE 1 A titanium-2% copper alloy is heated to a temperature of 800 C. for a period of 30 minutes and air cooled. The alloy is then reduced 10% by cold rolling and aged at 400 C. for 46 hours. After solution-treatment the Diamond Pyramid Hardness Numeral is 185, after cold rolling 233, and after ageing 272.

For comparison with the foregoing example, a hardness. of 259 is obtained when a similar alloy is solution-treated as in the example and aged for hours, but not cold worked after solution-treatment. Thus, in this example, the ageing time isv reduced by a factor of approximately 3 when the cold rolling step is added in accordance with theinvention.

The invention is applicable to the manufacture of a variety of products and articles formed from the titaniumbase alloy herein referred to, such as rod, forgings and,

Patented Mar. 28, 1961.

sheet, to cold roll and fabricate after solution-treatment and then to develop the improved properties subsequently by ageing.

8. A method of treating a titanium-base alloy consisting of between 1.8 and 2.2% copper, balance titanium apart from impurities, which comprises heating the alloy Table I Softening Anneal Solution Treatment Ageing Treatment Hardness (D.P.N.) Hard- Oomposition ness In- (inc. quality crernent mustrative of titanium) Temp., Time, Terminated Temp., Termi- Temp., Time, Terminated Solu- (per- 0. hr. by- C. Time nated 0. hr. bytion Aged cent) by- Treated 400 224 Quench... 185 224 21 400 224 do...-. 255 280 ggf g 400 224 do.. 203 264 31 400 230 --.do 128 223 74 Effect of interstitial impurity titanium content.

2.0% Cu 1,000 %hr ..do- 400 230 do... 253 288 12 Effect of solutiontreatment temperature.

2.0% Cu 700 1 Air cool.-- 800 10 min ---do..... 400 238 -.--.do... 195 280 41 Efiects of softening anneal and of solanon-treatment 2.0% Cu 800 1hr...-- Air cool. 400 238 Air cool... 203 275 Effect of terminating heat treatments by air cooling. 2.0% Cu 800 1hr. Quench 400 730 Quench--. 203 275 35 Effect of prolonged ageing time.

Table II Tensometer Elongation Percent Re- Percent In- Condition of Alloy Hardness U.T.S. Yield Pt. (percent on duction in crease in N.) (ton/sq. in.) (ton/sq. in.) I Area U.T.S. on

44 ageing Solution-treated 186 38. 2 30. 2 29 50-55 Aged 265 52. 9 45. 6 24 30 38 We claim: 1. A method of treating a titanium-base alloy consisting of between 0.9% and 2.6% copper, balance titanium 40 apart from impurities, which comprises heating the alloy to a temperature between 750 C. and 1000 C. for a period of not less than 5 minutes and cooling the alloy at a rate snfficient to retain the alloy constituents in solid solution, cold-working the alloy to effect a reduction of between 2% and 25%, and heating the alloy to a temperature between 300 C. and 600 C. for a period between 10 and 1000 hours.

2. A titanium-base alloy produced by the method of claim 1.

3. A method of treating a titanium-base alloy consisting of between 1.8% and 2.2% copper, balance titanium apart from impurities, which comprises heating the alloy to a temperature between 780 C. and 810 C. for a period between 10 minutes and 1 hour, cooling the alloy in air substantially to room temperature, cold-rolling the alloy to effect a reduction of between 2% and 25%, and heating the alloy to a temperature between 350 C. and 450 C. for a period between 10 and 300 hours.

'4. A titanium-base alloy produced by the method of claim 3.

5. A method of treating a titanium-base alloy consisting of between 0.9% and 2.6% copper, balance titanium apart from impurities, which comprises heating the alloy at a temperature between 750 C. and 1000" C. for a period of not less than 5 minutes, cooling the alloy at a rate sufficient to retain the alloy constituents. in solid solution and age-hardening the alloy by heating at a temperature between 300 C. and 600 C. for a period between 20 and 1000 hours.

6. A titanium-base alloy produced by the method of claim 5.

I 7. A method of treating a titanium-base alloy as set forth in claim 5 in which the age-hardening heat-treatment is carried out for about 160 to 320 hours.

to a temperature between 780 C. and 810 C. for a period between 10 minutes and 1 hour, cooling the alloy in air substantially to room temperature, and heating the alloy to a temperature between 350 C. and 450 C. for a period between 20 and 300 hours.

9. A titanium-base alloy produced by the method of claim 8.

10. A method of treating a titanium-base alloy consisting of between.1.8 and 2.2% copper, balance titanium apart from impurities which comprises heating the alloy to a temperature between 780 C. and 810 C. for a period between-10 minutes and 1 hour, cooling the alloy in air substantially to room temperature, and heating the alloy to a temperature between 350 C. and 450 C. for a period between and 320 hours.

References Cited in the file of this patent UNITED STATES PATENTS Jaffee et al Euly 2, 1957 Vordahl Oct. 21, 1958 OTHER REFERENCES Titanium Project PB 103370, The Manufacture of Ductile Ti and Ti Alloys, Report No. 17; period covered Apr. 1, 1947 to Sept. 1, 1948; page 35; released June 15, 1951.

Handbook. on Titanium, H. K. Adenstedt, August 1954; Wright. Air Development Center, WADC Technical Report 54-305, part 1, pages 11-2-1 and 11-2-2, 11-3-1 to 11-3-19.

Hansen: Constitution of Binary Alloys, McGraw-Hill, pages 642-646, 1958.

Titanium, McQuillan and McQuillan, pages 362-363, 372-378, 1956.

Physical Metallurgy and Heat Treatment of Titanium Alloys, Mallory Sharon Ti Corp., pages 11-25, 1955.

. The Iron'Age, pages 162-168, Apr. 2, 1953. 

5. A METHOD OF TREATING A TITANIUM-BASE ALLOY CONSISTING OF BETWEEN 0.9% AND 2.6% COPPER, BALANCE TITANIUM APART FROM IMPURITIES, WHICH COMPRISES HEATING THE ALLOY AT A TEMPERATURE BETWEEN 750*C. AND 1000*C. FOR A PERIOD OF NOT LESS THAN 5 MINUTES, COOLING THE ALLOY AT A RATE SUFFICIENT TO RETAIN THE ALLOY CONSTITUENTS IN SOLID SOLUTION AND AGE-HARDENING THE ALLOY BY HEATING AT A TEMPERATURE BETWEEN 300*C. AND 600*C. FOR A PERIOD BETWEEN 20 AND 1000 HOURS. 